Semiconductor integrated circuit

ABSTRACT

A semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell, the standard cell has: a p-type MOS transistor having first diffused regions and a first gate electrode; an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines; dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-129537, filed on May 15, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor integrated circuit having a standard cell used for a cell-base design.

2. Background Art

In recent years, Shallow Trench Isolation (STI) for device isolation has been used in CMOS processes. It is known that because of finer design rules in the CMOS processes, the threshold values of CMOS transistors are affected by stresses caused by STI.

For example, the shorter the distance from STI to the channel of a MOS transistor, the greater the stress of STI on the channel. Thus the current driving capability of an n-type MOS transistor decreases and the current driving capability of a p-type MOS transistor increases. In other words, it is difficult to predict the performance of a formed MOS transistor.

In order to avoid the influence of a stress caused by STI, it is necessary to increase a distance from STI to the channel of the MOS transistor.

However, a long distance from STI to the channel of the MOS transistor results in a large cell layout.

In the case where a semiconductor integrated circuit is designed by combining a plurality of function blocks called standard cells having uniform heights and power supply wiring configurations, it is difficult to increase the distance from STI to the channel to avoid the influence of a stress caused by STI.

In some conventional semiconductor integrated circuits, dummy MOS transistors are used for device isolation (for example, see U.S. Pat. No. 4,570,176).

However, the conventional art is not premised on standard cells or is not devised in consideration of the influence of a stress caused by STI or leak current of the dummy MOS transistors.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided: a semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell,

the standard cell comprising:

a p-type MOS transistor having first diffused regions and a first gate electrode;

an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines;

dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and

dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors,

wherein an absolute value of threshold voltage of the dummy p-type MOS transistor is higher than an absolute value of threshold voltage of the p-type MOS transistor, and

an absolute value of threshold voltage of the dummy n-type MOS transistor is higher than an absolute value of threshold voltage of the n-type MOS transistor.

According to the other aspect of the present invention, there is provided: a semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell,

the standard cell comprising:

a p-type MOS transistor having first diffused regions and a first gate electrode;

an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines;

dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and

dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors,

wherein the dummy p-type MOS transistor has a gate length greater than a gate length of the p-type MOS transistor, and

the dummy n-type MOS transistor has a gate length greater than a gate length of the n-type MOS transistor.

According to further aspect of the present invention, there is provided: a semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell,

the standard cell comprising:

a p-type MOS transistor having first diffused regions and a first gate electrode;

an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines;

dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and

dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors,

wherein the third gate electrodes of the dummy p-type MOS transistors are connected to the power supply wiring formed on a wiring layer disposed above a layer in which the third gate electrodes are formed, and

the fourth gate electrodes of the dummy n-type MOS transistors are connected to the ground wiring formed on a wiring layer disposed above a layer in which the fourth gate electrodes are formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the main configuration of a semiconductor integrated circuit 100 according to a first embodiment which is an aspect of the present invention;

FIG. 2 is a circuit diagram showing the circuit configuration of a standard cell of the semiconductor integrated circuit 100 shown in FIG. 1;

FIG. 3 shows the main configuration of a semiconductor integrated circuit 200 according to a second embodiment of the present invention;

FIG. 4 shows the main configuration of a semiconductor integrated circuit 300 according to a third embodiment of the present invention;

FIG. 5 shows the main configuration of a semiconductor integrated circuit 400 according to a fourth embodiment of the present invention;

FIG. 6 shows the main configuration of a semiconductor integrated circuit 200 a according to a fifth embodiment of the present invention;

FIG. 7 shows the main configuration of a semiconductor integrated circuit 500 according to a sixth embodiment which is an aspect of the present invention;

FIG. 8 is a circuit diagram showing the circuit configuration of the standard cell of the semiconductor integrated circuit 500 shown in FIG. 7;

FIG. 9 shows the main configuration of a semiconductor integrated circuit 600 according to a seventh embodiment of the present invention;

FIG. 10 shows the main configuration of a semiconductor integrated circuit 700 according to an eighth embodiment which is an aspect of the present invention;

FIG. 11 is a circuit diagram showing the circuit configuration of the standard cell of the semiconductor integrated circuit 700 shown in FIG. 10; and

FIG. 12 shows the main configuration of a semiconductor integrated circuit 800 according to a ninth embodiment of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will now be described in accordance with the accompanying drawings.

First Embodiment

FIG. 1 shows the main configuration of a semiconductor integrated circuit 100 according to a first embodiment which is an aspect of the present invention. FIG. 2 is a circuit diagram showing the circuit configuration of a standard cell of the semiconductor integrated circuit 100 shown in FIG. 1.

As shown in FIG. 1, the semiconductor integrated circuit 100 has a substantially rectangular standard cell 1 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 1, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 1. In other words, in FIG. 1, the first borderlines 100 a laterally extend and the second borderlines 100 b longitudinally extend.

In FIG. 1, the detailed configurations of the standard cells 1 a and 1 b are omitted for the sake of simplicity (the same hereinafter). For example, the standard cell 1 a and the standard cell 1 b are identical in configuration to the standard cell 1.

The standard cell 1 includes a p-type MOS transistor 4 which has first diffused regions 2 and a first gate electrode 3 and an n-type MOS transistor 8 which has second diffused regions 5 and a second gate electrode 6 with STI 7 disposed for device isolation between the p-type MOS transistor 4 and the n-type MOS transistor 8 substantially in parallel with the first borderlines 100 a.

As shown in FIGS. 1 and 2, the p-type MOS transistor 4 has the source connected to power supply wiring 101 via a contact 2 a, the drain connected to an output Z via a contact 2 b, and the gate connected to an input A.

The n-type MOS transistor 8 has the source connected to ground wiring 102 via a contact 5 a, the drain connected to the output Z and the drain of the p-type MOS transistor 4 via a contact 5 b, and the gate connected to the input A and the gate of the p-type MOS transistor 4.

As described above, in FIGS. 1 and 2, the standard cell 1 includes the layout of an inverter made up of the p-type MOS transistor 4 and the n-type MOS transistor 8.

Further, the standard cell 1 includes dummy p-type MOS transistors 10 a and 10 b for device isolation between the standard cell 1 and the standard cells 1 b that are adjacent to the standard cell 1 through the second borderlines 100 b. The dummy p-type MOS transistors 10 a and 10 b include third gate electrodes 9 a and 9 b which are disposed on the second borderlines 100 b so as to be adjacent to the first diffused regions 2 of the p-type MOS transistor 4.

In this configuration, the power supply wiring 101 is formed on, for example, a wiring layer disposed above a wiring layer in which the third gate electrodes 9 a and 9 b are formed.

The third gate electrodes 9 a and 9 b of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply wiring 101 via first contacts 13 a and 13 b that are connected to the ends of the third gate electrodes 9 a and 9 b at the center of the standard cell 1. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

The absolute values of threshold voltages of the dummy p-type MOS transistors 10 a and 10 b are set higher than the absolute value of threshold voltage of the p-type MOS transistor 4. Thus the dummy p-type MOS transistors 10 a and 10 b are turned off with higher reliability than the p-type MOS transistor 4. In other words, it is possible to suppress leakage current between the standard cell 1 and the standard cells 1 b that are adjacent to the standard cell 1 through the second borderlines 100 b.

In order to suppress the leakage current, the gate lengths of the dummy p-type MOS transistors 10 a and 10 b may be set longer than the gate length of the p-type MOS transistor 4.

The standard cell 1 further includes dummy n-type MOS transistors 12 a and 12 b for device isolation between the standard cell 1 and the standard cells 1 b that are adjacent to the standard cell 1 through the second borderlines 100 b. The dummy n-type MOS transistors 12 a and 12 b have fourth gate electrodes 11 a and 11 b disposed on the second borderlines 100 b so as to be adjacent to the second diffused regions 5 of the n-type MOS transistor 8.

In this configuration, the ground wiring 102 is formed on, for example, a wiring layer disposed above a wiring layer in which the fourth gate electrodes 11 a and 11 b are formed.

The fourth gate electrodes 11 a and 11 b of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground wiring 102 via second contacts 14 a and 14 b that are connected to the ends of the fourth gate electrodes 11 a and 11 b at the center of the standard cell 1. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

The absolute values of threshold voltages of the dummy n-type MOS transistors 12 a and 12 b are set higher than the absolute value of threshold voltage of the n-type MOS transistor 8. Thus the dummy n-type MOS transistors 12 a and 12 b are turned off with higher reliability than the n-type MOS transistor 8. In other words, it is possible to suppress leakage current between the standard cell 1 and the standard cells 1 b that are adjacent to the standard cell 1 through the second borderlines 100 b.

In order to suppress the leakage current, the gate lengths of the dummy n-type MOS transistors 12 a and 12 b may be set longer than the gate length of the n-type MOS transistor 8.

As described above, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND. Thus the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 100 configured thus, the standard cell 1 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Further, since the dummy MOS transistors are provided on the borderlines of the standard cell, the diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

As described above, the standard cell 1 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, for example, when a distance from STI to the channel of the MOS transistor (the width of the diffused region) is 2 μm or less, a large stress is caused by STI on the channel.

Therefore, for example, distances “X” (the widths of the diffused regions) are set at 2 μm or less between the first gate electrode 3 of the p-type MOS transistor 4 and the third gate electrodes 9 a and 9 b of the dummy p-type MOS transistors 10 a and 10 b. Similarly, for example, distances “X” are set at 2 μm or less between the second gate electrode 6 of the n-type MOS transistor 8 and the fourth gate electrodes 11 a and 11 b of the dummy n-type MOS transistors 12 a and 12 b.

Thus device isolation can be achieved by the dummy MOS transistors particularly in a range where device isolation by STI may cause a stress affecting the channel (the diffused region has a width of 2 μm or less), so that the stress can be avoided.

When the dummy MOS transistors have disadvantageous gate leakage current, the gate leakage can be avoided at least by forming the gates using a high dielectric material.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors.

Second Embodiment

The first embodiment described an example of a standard cell including an inverter made up of MOS transistors.

The present embodiment will describe another example of a standard cell including an inverter made up of MOS transistors.

FIG. 3 shows the main configuration of a semiconductor integrated circuit 200 according to a second embodiment of the present invention.

In FIG. 3, the same reference numerals as those of FIG. 1 indicate the same configurations as those of the first embodiment. Further, in FIG. 3, the circuit configuration of the standard cell of the semiconductor integrated circuit 200 is identical to the circuit configuration of the circuit diagram shown in FIG. 2.

As shown in FIG. 3, the semiconductor integrated circuit 200 has a substantially rectangular standard cell 201 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 201, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 201. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 201 and the other standard cells 1 b laterally adjacent to the standard cell 201 are identical in configuration to the standard cell 201.

The standard cell 201 is identical in configuration to the standard cell 1 of the first embodiment except for the layout of first and second contacts.

To be specific, first contacts 213 a and 213 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to a p-type MOS transistor 4. Similarly, second contacts 214 a and 214 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to an n-type MOS transistor 8.

Further, third gate electrodes 9 a and 9 b of dummy p-type MOS transistors 10 a and 10 b are connected to power supply wiring 101 via the first contacts 213 a and 213 b connected to the third gate electrodes 9 a and 9 b. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

Similarly, fourth gate electrodes 11 a and 11 b of dummy n-type MOS transistors 12 a and 12 b are connected to ground wiring 102 via second contacts 214 a and 214 b connected to the fourth gate electrodes 11 a and 11 b. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

Thus the gate voltages of the dummy MOS transistors can be directly supplied from, for example, the power supply wiring 101 and the ground wiring 102 which are provided near the first borderlines 100 a.

As described above, as in the first embodiment, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 200 configured thus, the standard cell 201 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cells, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 201 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the first embodiment.

Third Embodiment

The first and second embodiments described examples of a standard cell including an inverter made up of MOS transistors.

The present embodiment will describe still another example of a standard cell including an inverter made up of MOS transistors.

FIG. 4 shows the main configuration of a semiconductor integrated circuit 300 according to a third embodiment of the present invention.

In FIG. 4, the same reference numerals as those of FIG. 1 indicate the same configurations as those of the first embodiment. Further, in FIG. 4, the circuit configuration of the standard cell of the semiconductor integrated circuit 300 is identical to the circuit configuration of the circuit diagram shown in FIG. 2.

As shown in FIG. 4, the semiconductor integrated circuit 300 has a substantially rectangular standard cell 301 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 301, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 301. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 301 and the other standard cells 1 b laterally adjacent to the standard cell 301 are identical in configuration to the standard cell 301.

The standard cell 301 is identical in configuration to the standard cell 1 of the first embodiment except for the layout of first and second contacts.

To be specific, first contacts 313 a and 313 b are connected to the central portions of third gate electrodes 9 a and 9 b. Similarly, second contacts 314 a and 314 b are connected to the central portions of fourth gate electrodes 11 a and 11 b.

Further, the third gate electrodes 9 a and 9 b of dummy p-type MOS transistors 10 a and 10 b are connected to power supply wiring 101 via the first contacts 313 a and 313 b connected to the third gate electrodes 9 a and 9 b. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

Similarly, the fourth gate electrodes 11 a and 11 b of dummy n-type MOS transistors 12 a and 12 b are connected to ground wiring 102 via the second contacts 314 a and 314 b connected to the fourth gate electrodes 11 a and 11 b. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

As described above, as in the first embodiment, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 300 configured thus, the standard cell 301 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 301 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the first embodiment.

Fourth Embodiment

The first to third embodiments described examples of a standard cell including an inverter made up of MOS transistors.

The present embodiment will describe still another example of a standard cell including an inverter made up of MOS transistors.

FIG. 5 shows the main configuration of a semiconductor integrated circuit 400 according to a fourth embodiment of the present invention.

In FIG. 5, the same reference numerals as those of FIG. 1 indicate the same configurations as those of the first embodiment. Further, in FIG. 5, the circuit configuration of the standard cell of the semiconductor integrated circuit 400 is identical to the circuit configuration of the circuit diagram shown in FIG. 2.

As shown in FIG. 5, the semiconductor integrated circuit 400 has a substantially rectangular standard cell 401 which is divided by first borderlines 100 a opposed to other standard cells la longitudinally adjacent to the standard cell 401, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 401. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 401 and the other standard cells 1 b laterally adjacent to the standard cell 401 are identical in configuration to the standard cell 401.

The standard cell 401 is identical in configuration to the standard cell 1 of the first embodiment except for the layout of first and second contacts.

To be specific, first contacts 413 a and 413 b are connected to the ends of third gate electrodes 9 a and 9 b on the side of the first borderline 100 a. Similarly, second contacts 414 a and 414 b are connected to the ends of fourth gate electrodes 11 a and 11 b on the side of the first borderline 100 a.

Further, the third gate electrodes 9 a and 9 b of dummy p-type MOS transistors 10 a and 10 b are connected to power supply wiring 101 via the first contacts 413 a and 413 b connected to the third gate electrodes 9 a and 9 b. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

Similarly, the fourth gate electrodes 11 a and 11 b of dummy n-type MOS transistors 12 a and 12 b are connected to ground wiring 102 via the second contacts 414 a and 414 b connected to the fourth gate electrodes 11 a and 11 b. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

As described above, as in the first embodiment, the gates of dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 400 configured thus, the standard cell 401 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 401 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the first embodiment.

Fifth Embodiment

The second embodiment described an example of a standard cell including an inverter made up of MOS transistors.

The present embodiment will describe an example of a configuration in which standard cells having the same configurations as the standard cell of the second embodiment are adjacent to each other through a first borderline.

FIG. 6 shows the main configuration of a semiconductor integrated circuit 200 a according to a fifth embodiment of the present invention.

In FIG. 6, the same reference numerals as those of FIG. 2 indicate the same configurations as those of the second embodiment. Further, in FIG. 6, the circuit configuration of the standard cell of the semiconductor integrated circuit 200 a is identical to the circuit configuration of the circuit diagram shown in FIG. 2.

As shown in FIG. 6, the semiconductor integrated circuit 200 a has a substantially rectangular standard cell 201 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 201, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 201. In the present embodiment, at least the other standard cells 1 a longitudinally adjacent to the standard cell 201 are identical in configuration to the standard cell 201 (represented as standard cells 201 in FIG. 6).

As in the second embodiment, first contacts 213 a and 213 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to p-type MOS transistors 4. Similarly, second contacts 214 a and 214 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to n-type MOS transistors 8.

Therefore, as shown in FIG. 6, the standard cells 201 adjacent to each other through the first borderline 100 a share the first contacts 213 a and 213 b. Thus the layout area can be reduced.

The standard cells 201 adjacent to each other through the first borderline 100 a may be disposed to share the second contacts 214 a and 214 b.

In the semiconductor integrated circuit 200 a, as in the second embodiment, the gates of dummy p-type MOS transistors 10 a and 10 b are connected to a power supply potential VDD and the gates of dummy n-type MOS transistors 12 a and 12 b are connected to a ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 200 a configured thus, the standard cell 201 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cells 201 longitudinally adjacent to each other are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the second embodiment.

Sixth Embodiment

The first to fifth embodiments described examples of a standard cell including an inverter made up of MOS transistors.

The present embodiment will describe an example of a standard cell including a two-input NAND circuit made up of MOS transistors.

FIG. 7 shows the main configuration of a semiconductor integrated circuit 500 according to a sixth embodiment which is an aspect of the present invention. FIG. 8 is a circuit diagram showing the circuit configuration of the standard cell of the semiconductor integrated circuit 500 shown in FIG. 7.

As shown in FIG. 7, the semiconductor integrated circuit 500 has a substantially rectangular standard cell 501 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 501, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 501. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 501 and the other standard cells 1 b laterally adjacent to the standard cell 501 are identical in configuration to the standard cell 501.

The standard cell 501 includes a first p-type MOS transistor 4 a which has first diffused regions 502 a and 502 b and a first gate electrode 3 a and a second p-type MOS transistor 4 b which has the first diffused region 502 b, a first diffused region 502 c, and a first gate electrode 3 b.

Further, the standard cell 501 includes a first n-type MOS transistor 8 a which has second diffused regions 505 a and 505 b and a second gate electrode 6 a and a second n-type MOS transistor 8 b which has the second diffused region 505 b, a second diffused region 505 c, and a second gate electrode 6 b.

The first and second n-type MOS transistors 8 a and 8 b have STI 7 disposed for device isolation between the first and second n-type MOS transistors 8 a and 8 b and the first and second p-type MOS transistors 4 a and 4 b substantially in parallel with the first borderlines 100 a.

As shown in FIGS. 7 and 8, the first and second p-type MOS transistors 4 a and 4 b have the sources connected to power supply wiring 101 via contacts 2 a, the drains connected to an output Z via a contact 2 b, and the gates connected to inputs A and B, respectively.

The first n-type MOS transistor 8 a has the source connected to ground wiring 102 via a contact 5 a, the drain connected to the source of the second n-type MOS transistor 8 b, and the gate connected to the input A and the gate of the first p-type MOS transistor 4 a.

The second n-type MOS transistor 8 b has the drain connected to the output Z and the drains of the first and second p-type MOS transistors 4 a and 4 b via the contact 5 b, and the gate connected to the input B and the gate of the second p-type MOS transistor 4 b.

In this way, in FIGS. 7 and 8, the standard cell 501 includes an NAND layout of two inputs (A, B) made up of the first and second p-type MOS transistors 4 a and 4 b and the first and second n-type MOS transistors 8 a and 8 b.

Further, as in the first embodiment, the standard cell 501 includes dummy p-type MOS transistors 10 a and 10 b for device isolation between the standard cell 501 and the standard cells 1 b that are adjacent to the standard cell 501 through the second borderlines 100 b. The dummy p-type MOS transistors 10 a and 10 b include third gate electrodes 9 a and 9 b which are disposed on the second borderlines 100 b so as to be adjacent to the first diffused regions 502 a and 502 c of the first and second p-type MOS transistors 4 a and 4 b.

In this configuration, the power supply wiring 101 is formed on, for example, a wiring layer disposed above a wiring layer in which the third gate electrodes 9 a and 9 b are formed.

As in the first embodiment, the third gate electrodes 9 a and 9 b of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply wiring 101 via the first contacts 513 a and 513 b that are connected to the ends of the third gate electrodes 9 a and 9 b at the center of the standard cell 501. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

As in the first embodiment, the absolute values of threshold voltages of the dummy p-type MOS transistors 10 a and 10 b are set higher than the absolute values of threshold voltages of the first and second p-type MOS transistors 4 a and 4 b. Thus the dummy p-type MOS transistors 10 a and 10 b are turned off with higher reliability than the first and second p-type MOS transistors 4 a and 4 b. In other words, it is possible to suppress leakage current between the standard cell 501 and the standard cells 1 b that are adjacent to the standard cell 501 through the second borderlines 100 b.

Further, as in the first embodiment, the gate lengths of the dummy p-type MOS transistors 10 a and 10 b may be set longer than the gate lengths of the first and second p-type MOS transistors 4 a and 4 b in order to suppress the leakage current.

Moreover, the standard cell 501 includes dummy n-type MOS transistors 12 a and 12 b for device isolation between the standard cell 501 and the standard cells 1 b that are adjacent to the standard cell 501 through the second borderlines 100 b. The dummy n-type MOS transistors 12 a and 12 b include fourth gate electrodes 11 a and 11 b which are disposed on the second borderlines 100 b so as to be adjacent to the second diffused regions 505 a and 505 c of the first and second n-type MOS transistors 8 a and 8 b.

In this configuration, the ground wiring 102 is formed on, for example, a wiring layer disposed above a wiring layer in which the fourth gate electrodes 11 a and 11 b are formed.

As in the first embodiment, the fourth gate electrodes 11 a and 11 b of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground wiring 102 via second contacts 514 a and 514 b that are connected to the ends of the fourth gate electrodes 11 a and 11 b at the center of the standard cell 501. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

As in the first embodiment, the absolute values of threshold voltages of the dummy n-type MOS transistors 12 a and 12 b are set higher than the absolute values of threshold voltages of the first and second n-type MOS transistors 8 a and 8 b. Thus the dummy n-type MOS transistors 12 a and 12 b are turned off with higher reliability than the first and second n-type MOS transistors 8 a and 8 b. In other words, it is possible to suppress leakage current between the standard cell 501 and the standard cells 1 b that are adjacent to the standard cell 501 through the second borderlines 100 b.

Further, the gate lengths of the dummy n-type MOS transistors 12 a and 12 b may be set longer than the gate lengths of the first and second n-type MOS transistors 8 a and 8 b in order to suppress the leakage current.

As described above, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 500 configured thus, the standard cell 501 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy transistors are provided on the borderlines of the standard cell, the diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

As described above, the standard cell 501 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As in the first embodiment, for example, distances “X” (the widths of the diffused regions) are set at 2 μm or less between the first gate electrode 3 a of the first p-type MOS transistor 4 a and the third gate electrode 9 a of the dummy p-type MOS transistor 10 a and between the first gate electrode 3 b of the second p-type MOS transistor 4 b and the third gate electrode 9 b of the dummy p-type MOS transistor 10 b. Similarly, for example, distances “X” are set at 2 μm or less between the second gate electrode 6 a of the first n-type MOS transistor 8 a and the fourth gate electrode 11 a of the dummy n-type MOS transistor 12 a and between the second gate electrode 6 b of the second n-type MOS transistor 8 b and the fourth gate electrode of the dummy n-type MOS transistor 12 b.

Thus device isolation can be achieved by the dummy MOS transistors particularly in a range where device isolation by STI may cause a stress affecting the channel (the diffused region has a width of 2 μm or less), so that the stress can be avoided.

When the dummy MOS transistors have disadvantageous gate leakage current, the gate leakage can be avoided at least by forming the gates using a high dielectric material.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors.

Seventh Embodiment

The sixth embodiment described an example of a standard cell including a two-input NAND circuit made up of MOS transistors.

The present embodiment will describe another example of a standard cell including a two-input NAND circuit made up of MOS transistors.

FIG. 9 shows the main configuration of a semiconductor integrated circuit 600 according to a seventh embodiment of the present invention.

In FIG. 9, the same reference numerals as those of FIG. 7 indicate the same configurations as those of the sixth embodiment. Further, in FIG. 9, the circuit configuration of the standard cell of the semiconductor integrated circuit 600 is identical to the circuit configuration of the circuit diagram shown in FIG. 8.

As shown in FIG. 9, the semiconductor integrated circuit 600 has a substantially rectangular standard cell 601 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 601, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 601. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 601 and the other standard cells 1 b laterally adjacent to the standard cell 601 are identical in configuration to the standard cell 601.

The standard cell 601 is identical in configuration to the standard cell 501 of the sixth embodiment except for the layout of first and second contacts.

To be specific, first contacts 613 a and 613 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to first and second p-type MOS transistors 4 a and 4 b. Similarly, second contacts 614 a and 614 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to first and second n-type MOS transistors 8 a and 8 b.

Further, third gate electrodes 9 a and 9 b of dummy p-type MOS transistors 10 a and 10 b are connected to power supply wiring 101 via the first contacts 613 a and 613 b connected to the third gate electrodes 9 a and 9 b. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

Similarly, fourth gate electrodes 11 a and 11 b of dummy n-type MOS transistors 12 a and 12 b are connected to ground wiring 102 via the second contacts 614 a and 614 b connected to the fourth gate electrodes 11 a and 11 b. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

Thus the gate voltages of the dummy MOS transistors can be directly supplied from, for example, the power supply wiring 101 and the ground wiring 102 which are provided near the first borderlines 100 a.

As described above, as in the sixth embodiment, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 600 configured thus, the standard cell 601 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 601 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the sixth embodiment.

Eighth Embodiment

The sixth and seventh embodiments described examples of a standard cell including a two-input NAND circuit made up of MOS transistors.

The present embodiment will describe an example of a standard cell including a two-input NOR circuit made up of MOS transistors.

FIG. 10 shows the main configuration of a semiconductor integrated circuit 700 according to an eighth embodiment which is an aspect of the present invention. FIG. 11 is a circuit diagram showing the circuit configuration of the standard cell of the semiconductor integrated circuit 700 shown in FIG. 10.

As shown in FIG. 10, the semiconductor integrated circuit 700 has a substantially rectangular standard cell 701 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 701, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 701. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 701 and the other standard cells 1 b laterally adjacent to the standard cell 701 are identical in configuration to the standard cell 701.

As in the sixth embodiment, the standard cell 701 includes a first p-type MOS transistor 4 a which has first diffused regions 502 a and 502 b and a first gate electrode 3 a and a second p-type MOS transistor 4 b which has the first diffused region 502 b, a first diffused region 502 c, and a first gate electrode 3 b.

Further, the standard cell 701 includes a first n-type MOS transistor 8 a which has second diffused regions 505 a and 505 b and a second gate electrode 6 a and a second n-type MOS transistor 8 b which has the second diffused region 505 b, a second diffused region 505 c, and a second gate electrode 6 b.

The first and second n-type MOS transistors 8 a and 8 b have STI 7 disposed for device isolation between the first and second n-type MOS transistors 8 a and 8 b and the first and second p-type MOS transistors 4 a and 4 b substantially in parallel with the first borderlines 100 a.

As shown in FIGS. 10 and 11, the first p-type MOS transistor 4 a has the source connected to power supply wiring 101 via a contact 2 a, the drain connected to the source of the second p-type MOS transistor 4 b, and the gate connected to an input A and the gate of the first n-type MOS transistor 8 a.

Further, the second p-type MOS transistor 4 b has the drain connected to an output Z and the drains of the first and second n-type MOS transistors 8 a and 8 b via a contact 2 b, and the gate connected to an input B and the gate of the second n-type MOS transistor 8 b.

The first and second n-type MOS transistors 8 a and 8 b have the sources connected to ground wiring 102 via contacts 5 a, the drains connected to the output Z via a contact 5 b, and the gates connected to the inputs A and B.

In this way, in FIGS. 10 and 11, the standard cell 701 includes an NOR layout of two inputs (A, B) made up of the first and second p-type MOS transistors 4 a and 4 b and the first and second n-type MOS transistors 8 a and 8 b.

Further, as in the sixth embodiment, the standard cell 701 includes dummy p-type MOS transistors 10 a and 10 b for device isolation between the standard cell 701 and the standard cells 1 b that are adjacent to the standard cell 701 through the second borderlines 100 b. The dummy p-type MOS transistors 10 a and 10 b include third gate electrodes 9 a and 9 b which are disposed on the second borderlines 100 b so as to be adjacent to first diffused regions 502 a and 502 c of the first and second p-type MOS transistors 4 a and 4 b respectively.

In this configuration, the power supply wiring 101 is formed on, for example, a wiring layer disposed above a wiring layer in which the third gate electrodes 9 a and 9 b are formed.

As in the sixth embodiment, the third gate electrodes 9 a and 9 b of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply wiring 101 via first contacts 713 a and 713 b that are connected to the ends of the third gate electrodes 9 a and 9 b at the center of the standard cell 701. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

As in the sixth embodiment, the absolute values of threshold voltages of the dummy p-type MOS transistors 10 a and 10 b are set higher than the absolute values of threshold voltages of the first and second p-type MOS transistors 4 a and 4 b. Thus the dummy p-type MOS transistors 10 a and 10 b are turned off with higher reliability than the first and second p-type MOS transistors 4 a and 4 b. In other words, it is possible to suppress leakage current between the standard cell 701 and the standard cells 1 b that are adjacent to the standard cell 701 through the second borderlines 100 b.

As in the sixth embodiment, the gate lengths of the dummy p-type MOS transistors 10 a and 10 b may be set longer than the gate lengths of the first and second p-type MOS transistors 4 a and 4 b in order to suppress the leakage current.

Further, the standard cell 701 includes dummy n-type MOS transistors 12 a and 12 b for device isolation between the standard cell 701 and the standard cells 1 b that are adjacent to the standard cell 701 through the second borderlines 100 b. The dummy n-type MOS transistors 12 a and 12 b include fourth gate electrodes 11 a and 11 b that are disposed on the second borderlines 100 b so as to be adjacent to the second diffused regions 505 a and 505 c of the first and second n-type MOS transistors 8 a and 8 b.

In this configuration, the ground wiring 102 is formed on, for example, a wiring layer disposed above a wiring layer in which the fourth gate electrodes 11 a and 11 b are formed.

As in the sixth embodiment, the fourth gate electrodes 11 a and 11 b of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground wiring 102 via second contacts 714 a and 714 b that are connected to the ends of the fourth gate electrodes 11 a and 11 b at the center of the standard cell 701. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

As in the sixth embodiment, the absolute values of threshold voltages of the dummy n-type MOS transistors 12 a and 12 b are set higher than the absolute values of threshold voltages of the first and second n-type MOS transistors 8 a and 8 b. Thus the dummy n-type MOS transistors 12 a and 12 b are turned off with higher reliability than the first and second n-type MOS transistors 8 a and 8 b. In other words, it is possible to suppress leakage current between the standard cell 701 and the standard cells 1 b that are adjacent to the standard cell 701 through the second borderlines 100 b.

Further, the gate lengths of the dummy n-type MOS transistors 12 a and 12 b may be set longer than the gate lengths of the first and second n-type MOS transistors 8 a and 8 b in order to suppress the leakage current.

As described above, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 700 configured thus, the standard cell 701 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, the diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 701 and the standard cells 1 a are isolated from each other, as described above, by STI provided along the first borderlines 100 a.

As in the sixth embodiment, for example, distances “X” (the widths of the diffused regions) are set at 2 μm or less between the first gate electrode 3 a of the first p-type MOS transistor 4 a and the third gate electrode 9 a of the dummy p-type MOS transistor 10 a and between the first gate electrode 3 b of the second p-type MOS transistor 4 b and the third gate electrode 9 b of the dummy p-type MOS transistor 10 b. Similarly, for example, distances “X” are set at 2 μm or less between the second gate electrode 6 a of the first n-type MOS transistor 8 a and the fourth gate electrode 11 a of the dummy n-type MOS transistor 12 a and between the second gate electrode 6 b of the second n-type MOS transistor 8 b and the fourth gate of the dummy n-type MOS transistor 12 b.

Thus device isolation can be achieved by the dummy MOS transistors particularly in a range where device isolation by STI may cause a stress affecting the channel (the diffused region has a width of 2 μm or less), so that the stress can be avoided.

When the dummy MOS transistors have disadvantageous gate leakage current, the gate leakage can be avoided at least by forming the gates using a high dielectric material.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors.

Ninth Embodiment

The eighth embodiment described an example of a standard cell including a two-input NOR circuit made up of MOS transistors.

The present embodiment will describe another example of a standard cell including a two-input NOR circuit made up of MOS transistors.

FIG. 12 shows the main configuration of a semiconductor integrated circuit 800 according to a ninth embodiment of the present invention.

In FIG. 12, the same reference numerals as those of FIG. 10 indicate the same configurations as those of the eighth embodiment. Further, in FIG. 12, the circuit configuration of the standard cell of the semiconductor integrated circuit 800 is identical to the circuit configuration of the circuit diagram shown in FIG. 11.

As shown in FIG. 12, the semiconductor integrated circuit 800 has a substantially rectangular standard cell 801 which is divided by first borderlines 100 a opposed to other standard cells 1 a longitudinally adjacent to the standard cell 801, and second borderlines 100 b opposed to other standard cells 1 b laterally adjacent to the standard cell 801. For example, the other standard cells 1 a longitudinally adjacent to the standard cell 801 and the other standard cells 1 b laterally adjacent to the standard cell 801 are identical in configuration to the standard cell 801.

The standard cell 801 is identical in configuration to the standard cell 701 of the eighth embodiment except for the layout of first and second contacts.

To be specific, first contacts 813 a and 813 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to first and second p-type MOS transistors 4 a and 4 b. Similarly, second contacts 814 a and 814 b are formed on the intersection points of the second borderlines 100 b and the first borderline 100 a disposed close to first and second n-type MOS transistors 8 a and 8 b.

Further, third gate electrodes 9 a and 9 b of dummy p-type MOS transistors 10 a and 10 b are connected to power supply wiring 101 via the first contacts 813 a and 813 b that are connected to the third gate electrodes 9 a and 9 b. Therefore, a power supply potential VDD is applied to the third gate electrodes 9 a and 9 b so as to turn off the dummy p-type MOS transistors 10 a and 10 b.

Similarly, fourth gate electrodes 11 a and 11 b of dummy n-type MOS transistors 12 a and 12 b are connected to ground wiring 102 via the second contacts 814 a and 814 b that are connected to the fourth gate electrodes 11 a and 11 b. Therefore, a ground potential GND is applied to the fourth gate electrodes 11 a and 11 b so as to turn off the dummy n-type MOS transistors 12 a and 12 b.

Thus the gate voltages of the dummy MOS transistors can be directly supplied from, for example, the power supply wiring 101 and the ground wiring 102 which are provided near the first borderlines 100 a.

As described above, as in the sixth embodiment, the gates of the dummy p-type MOS transistors 10 a and 10 b are connected to the power supply potential VDD and the gates of the dummy n-type MOS transistors 12 a and 12 b are connected to the ground potential GND, so that the transistors are turned off and insulation is provided between the standard cells that are adjacent to each other through the second borderlines 100 b.

As described above, in the semiconductor integrated circuit 800 configured thus, the standard cell 801 and the standard cells 1 b are isolated from each other by the dummy p-type MOS transistors 10 a and 10 b and the dummy n-type MOS transistors 12 a and 12 b which are provided on the second borderlines 100 b. Thus it is possible to reduce the influence of a stress on the MOS transistors at least in the directions of the first borderlines 100 a (in the channel directions of the MOS transistors).

Therefore, it is possible to avoid STI stress and increase the predictability of the on currents of the MOS transistors composing the standard cell.

Moreover, since the dummy MOS transistors are provided on the borderlines of the standard cell, diffused regions can be formed continuously from the other standard cells adjacent to the diffused regions.

The standard cell 801 and the standard cells 1 a are isolated from each other by STI provided along the first borderlines 100 a.

As described above, according to the semiconductor integrated circuit of the present embodiment, it is possible to achieve device isolation between the adjacent standard cells while avoiding the influence of the device isolation on the MOS transistors as in the eighth embodiment.

The aforementioned embodiments described, for example, inverters, two-input NAND circuits, and two-inputs NOR circuits. The present invention is similarly applicable to standard cells including typical CMOS logic circuits, in addition to the aforementioned circuit configurations.

In order to suppress leakage current in the aforementioned embodiments, for example, the absolute values of threshold voltages of the dummy MOS transistors for device isolation are set higher than the absolute values of threshold voltages of the typical MOS transistors disposed in the standard cell. The absolute values of threshold voltages of the dummy MOS transistors may be equal to the absolute values of threshold voltages of the typical MOS transistors when necessary. 

1. A semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell, the standard cell comprising: a p-type MOS transistor having first diffused regions and a first gate electrode; an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines; dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors, wherein an absolute value of threshold voltage of the dummy p-type MOS transistor is higher than an absolute value of threshold voltage of the p-type MOS transistor, and an absolute value of threshold voltage of the dummy n-type MOS transistor is higher than an absolute value of threshold voltage of the n-type MOS transistor.
 2. The semiconductor integrated circuit according to claim 1, wherein the power supply wiring is formed on a layer disposed above a layer in which the third gate electrodes are formed, the ground wiring is formed on a layer disposed above a layer in which the fourth gate electrodes are formed, the third gate electrodes of the dummy p-type MOS transistors are connected to the power supply wiring via first contacts, and the fourth gate electrodes of the dummy n-type MOS transistors are connected to the ground wiring via second contacts.
 3. The semiconductor integrated circuit according to claim 2, wherein the first contacts are formed on intersection points of the second borderlines and the first borderline disposed close to the p-type MOS transistor, and the second contacts are formed on intersection points of the second borderlines and the first borderline disposed close to the n-type MOS transistor.
 4. The semiconductor integrated circuit according to claim 1, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 5. The semiconductor integrated circuit according to claim 2, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 6. The semiconductor integrated circuit according to claim 3, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 7. A semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell, the standard cell comprising: a p-type MOS transistor having first diffused regions and a first gate electrode; an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines; dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors, wherein the dummy p-type MOS transistor has a gate length greater than a gate length of the p-type MOS transistor, and the dummy n-type MOS transistor has a gate length greater than a gate length of the n-type MOS transistor.
 8. The semiconductor integrated circuit according to claim 7, wherein the power supply wiring is formed on a layer disposed above a layer in which the third gate electrodes are formed, the ground wiring is formed on a layer disposed above a layer in which the fourth gate electrodes are formed, the third gate electrodes of the dummy p-type MOS transistors are connected to the power supply wiring via first contacts, and the fourth gate electrodes of the dummy n-type MOS transistors are connected to the ground wiring via second contacts.
 9. The semiconductor integrated circuit according to claim 8, wherein the first contacts are formed on intersection points of the second borderlines and the first borderline disposed close to the p-type MOS transistor, and the second contacts are formed on intersection points of the second borderlines and the first borderline disposed close to the n-type MOS transistor.
 10. The semiconductor integrated circuit according to claim 7, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 11. The semiconductor integrated circuit according to claim 8, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 12. The semiconductor integrated circuit according to claim 9, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less.
 13. A semiconductor integrated circuit having a substantially rectangular standard cell divided by first borderlines opposed to other standard cells longitudinally adjacent to the standard cell and second borderlines opposed to other standard cells laterally adjacent to the standard cell, the standard cell comprising: a p-type MOS transistor having first diffused regions and a first gate electrode; an n-type MOS transistor having second diffused regions and a second gate electrode with STI disposed for device isolation between the n-type MOS transistor and the p-type MOS transistor substantially in parallel with the first borderlines; dummy p-type MOS transistors having third gate electrodes disposed on the second borderlines so as to be adjacent to the first diffused regions of the p-type MOS transistor, the third gate electrodes being connected to power supply wiring so as to turn off the dummy p-type MOS transistors; and dummy n-type MOS transistors having fourth gate electrodes disposed on the second borderlines so as to be adjacent to the second diffused regions of the n-type MOS transistor, the fourth gate electrodes being connected to ground wiring so as to turn off the dummy n-type MOS transistors, wherein the third gate electrodes of the dummy p-type MOS transistors are connected to the power supply wiring formed on a wiring layer disposed above a layer in which the third gate electrodes are formed, and the fourth gate electrodes of the dummy n-type MOS transistors are connected to the ground wiring formed on a wiring layer disposed above a layer in which the fourth gate electrodes are formed.
 14. The semiconductor integrated circuit according to claim 13, wherein distances between the first gate electrode of the p-type MOS transistor and the third gate electrodes of the dummy p-type MOS transistors are 2 μm or less, and distances between the second gate electrode of the n-type MOS transistor and the fourth gate electrodes of the dummy n-type MOS transistors are 2 μm or less. 